The invention relates to a sealed forced-draft gas boiler, and more particularly to a novel disposition of the sealed enclosure provided for evacuating combustion products from the gas boiler.
Gas boilers are known in which a combustion chamber, connected to the atmosphere outside the premises, is insulated in a gas-tight manner with regard to these premises. In some cases such boilers are surrounded by an intermediate chamber serving to deliver air and enveloping the combustion chamber in a sealed manner, the latter being incorporated in turn in the external casing of the apparatus. In other known apparatus, the external casing of the apparatus itself embodies this sealed intermediate chamber, and the combustion products are evacuated from this combustion chamber by way of a hood, a blow off fan and an outlet pipe. It is known to be advantageous for the outlet pipe to be disposed concentrically with the fresh-air intake pipe.
Boilers are also known in which the heat exchanger comprises a cylindrical bundle of tubes interconnected by end headers; the heat exchanger defines a combustion chamber through which the flame of a burner passes, giving up its heat to the water circulating in the heat exchanger tubes. Certain preferred embodiments provide that this heat exchanger be disposed upright in the interior of an insulating casing, the burner being disposed just above the combustion chamber.
However, these boiler types nevertheless have a certain number of disadvantages in terms of their assembly, their accessibility and especially their tightness, because tightness must be assured at the points where gas or water tubes intersect, which creates a certain number of problems.